Improper Starter Engagement

[LTZ C20]

Better the bendix gear failed then the flex-plate/flywheel.

I've got a bad spot on my flex plate that shows up at the most inopportune times.

The bendix gear & flywheel both failed 3 starter replacements ago. That was when the very first starter destroyed itself and the ring gear. Replacement of the flexplate that was only 6 months old already is something we don't discuss because it will only aggravate me at the highest order, I almost put a 12 gauge slug threw the block that day......

Well now the 70's starter is installed with an extra heat shield I had and support brace that I fabricated, along with 2 new accessorie power wires that go to the positive cable stud. All works well 3 times in a row, but I keep starting it just to be sure.

During assembly, those 2 power wires had black chunks falling from inside their loom. So pulled the loom off and found this.


I cut the wires off where they were still good back behind the block and repaired them good and proper.

Here's the failed starter.

[blazer74]

Wow, serious amp draw or excessive heat.

[LTZ C20]

I think it was heat. I have headers and the delco starter above had no provisions for a heat shield. Now I have a heat shield, new wires, I routed them a little different and header wrap on the lower half of the header that's right by the starter. The wrap was there already but not anywhere near the time period those wires have been down there. The new routing has more airflow area and I can see them from the top so I'll keep an eye on them.

[bd]

LTZ, failure analysis is a vital component of success.  Take a few minutes and lay out all of the parts.  Look at them.  Inspect every detail.  Observe each failure, both independently and collectively.  Don't conclude anything until you have inspected everything.  Based only on what you see, what was (were) the cause(s)?

[LTZ C20]

BD, are we referring to the starter failure or the 2 damaged wires?

[bd]

BD, are we referring to the starter failure or the 2 damaged wires?

Both.

[LTZ C20]

Ok so here's what I saw.

Starter failer:
-starter gear stripped
-flywheel not stripped
-bolts where tight, no shims had fallen out (had 4 shims, I've read somewhere should be no more than 5 total)
-starter was a Delco gear reduction type, (more torque than a direct drive? Not sure on that)
-no provisions for a support bracket, so there was no bracket installed

Possible cause of failure:
Starter creates to much torque during cranking, the number of shims and no support bracket allowed the starter body to flex away from the flexplate and over time wear the gear down untill it stripped out completely. Gear lash was in spec when I installed it.

The new starter (a direct drive unit) has a support bracket, only 1 shim, bolts are torqued to spec, gear lash is in spec. It is working good so far.

Damaged wires:
-no heat shield
-wires were routed too close to header even tho they weren't close enough to flex and touch
-the loom was soaked in oil from a previous leak.
-no protective header wrap to help dissipate heat.

Possible cause of failure:
The previous oil leak soaked the loom in oil which over time soaked into the insulation of the wiring, degrading the material, along side being in the same area as an object which radiates high heat. The heat cooked the the oil which burnt the insulation to a crisp, destroying the wires. The exposed wiring turned gear due to exposure to atmosphere which could be wet or damp at times, oxidizing the exposed area.

The header now has heat wrap around the entire starter area, the oil leak was fixed, the wires routed with more air flow and room between them and the header, all of the oil soaked loom was removed and the wiring cut back where it was still good and repaired and reloomed.

Best as I can tell, that's what makes the most sense to me.